纳米钛酸锶粉体的制备及光催化研究

以乙酸锶和钛酸丁酯为前驱物,采用溶胶-凝胶法在低温下合成了高纯、超细SrTiO3粉体。采用扫描电镜及紫外吸收等测试手段,对制备的SrTiO3粉体的基本特性进行了表征,并对其光催化特性进行了研究。结果表明:随着热处理温度的升高,粉体的紫外吸收峰出现红移现象;降解率随时间的增加而增加,但随着光催化反应时间的延长,降解活性有所降低;800℃下钛酸锶粉体的甲基橙脱色率可达到78%。     

溶胶-凝胶法制备钛酸锶粉体及其光催化性能的研究

用溶胶-凝胶法制备钙钛矿型SrTiO₃粉体。并用自制的反应器,考察了SrTiO₃粉体对NOx的光催化脱除能力,研究了光源、气体初始浓度、湿度对光催化效果的影响。结果表明,经过45 min的光催化反应,不同浓度的气体中NOx的脱除率均在70%以上。     

纳米钛酸锶粉体的溶胶—凝胶法制备与研究

以硝酸锶和钛酸丁酯为原料,柠檬酸为络合剂,乙二醇为稳定剂,在液相中发生络合反应制备前驱物,再将前驱物干燥,烧结得到钛酸锶粉体,并对粉体进行XRD分析。经多组对比试验表明,pH值、用水量、柠檬酸用量对粉体的性质有比较明显的影响。     

钛酸锶粉体的制备及催化降解孔雀石绿废水

采用沉淀法制备钛酸锶粉体,通过XRD、SEM对产物进行表征。研究钛酸锶粉体对孔雀石绿废水的催化活性。对比了无钛酸锶的同样条件下,超声辅助双氧水降解孔雀石绿的效果。探讨了钛酸锶催化剂的投加量、时间等对催化效果的影响。结果表明,钛酸锶用量为0.1g,氧化剂双氧水滴加0.5mL,100mL浓度为30mg/L的孔雀石绿废水超声10min降解率可达97.8%。超声辅助钛酸锶-H2O2体系催化降解孔雀石绿废水效果好。对降解三苯甲烷类染料废水有一定实用参考意义。     

La+掺杂纳米TiO2薄膜的制备及降解烟雾性能研究

以钛酸丁酯为原料采用溶胶凝胶法制备了金属镧离子掺杂的纳米二氧化钛溶胶通过拉提-浸渍的方法将其负载到载玻片上,并利用X射线衍射(XRD)和扫描电子显微镜(SEM)对薄膜进行表征。研究了镀膜层数,焙烧温度对薄膜的晶型、表面形貌及吸附降解香烟烟雾性能的影响。结果表明,经过500℃热处理后的适量掺杂镧离子的二氧化钛主要以锐钛矿晶型存在,在紫外光照射下对香烟烟雾有很好的吸附降解作用。     

溶胶-凝胶法制备钛酸锶钡铁电薄膜的研究

钛酸锶钡(BST)薄膜是一类重要的铁电薄膜材料。采用溶胶-凝胶法制备了不同组分的具有钙钛矿结构的BST薄膜。利用X射线衍射技术(XRD),研究了不同退火条件下BST薄膜的结晶特性,结果表明制备的BST薄膜形成了单一的钙钛矿结构;利用扫描电子显微镜(SEM)和原子力显微镜(AFM)观察了薄膜的表面形貌,结果表明制备的BST薄膜光滑,平整,无明显的孔洞和裂纹,且生长良好。BST薄膜的晶粒细致,排列整齐,分布均匀,呈现球状。     

掺铁纳米二氧化钛的的制备及光催化性能

以钛酸丁酯为原料,采用溶胶-凝胶法制备出了掺杂Fe的纳米二氧化钛粉体。采用紫外-可见漫反射吸收光谱（DRS）和X射线衍射（XRD）技术对其进行表征,并对Fe掺杂浓度、煅烧温度、煅烧时间对纳米TiO2光学活性的影响进行了研究。研究结果表明,掺杂0.5%Fe,煅烧温度500℃,煅烧时间2h改性的粉体其可见光范围的吸收明显增强,降解邻氨基苯酚的能力明显提高,5h后可达85%以上。     

N、Mo共掺杂TiO_2光催化剂的制备及对亚甲基蓝降解性能研究

以硫脲、钼酸铵和钛酸四丁酯为原料,利用溶胶-凝胶法制备了未掺杂的和N、Mo共掺杂的TiO2光催化剂。用紫外-可见吸收光谱对制备的催化剂样品进行了表征,考察了不同条件下光催化剂对亚甲基蓝溶液的光催化活性。试验结果表明,N、Mo共掺杂使TiO2催化剂的吸收带边位置发生了红移;在可见光条件下,0.125 gN、Mo共掺杂TiO2(n(N)∶n(Mo)=2∶1)、pH值为6.20、温度为30℃的体系对质量浓度为20 mg/L的亚甲基蓝溶液的脱色效果最好。     

N、Bi共掺杂TiO_2光催化剂的制备及对靛红降解性能研究

以硫脲为氮源,硝酸铋为铋源,钛酸四正丁酯为原料,利用溶胶-凝胶法制备了纯TiO2和不同比例N、Bi共掺杂的TiO2光催化剂样品。用紫外-可见分光光度仪对制备的催化剂样品进行了表征。结果表明,制备的N、Bi共掺杂TiO2纳米粉体在可见光区吸收红移,表现出优异的光催化性能;当N与Bi的物质的量比为8∶1、反应温度为25℃,底物的质量浓度为20 mg/L、pH值为5.0时,该光催化体系对靛红溶液的脱色效果最好,脱色率最高为23%。     

单相钛酸锶粉体的制备研究

采用SEM、XRD及FT-IR研究了碳酸锶和二氧化钛(锐钛矿)经高能球磨后的结构变化,讨论了单相钛酸锶的形成机理.SEM和XRD研究表明,高能球磨破坏了原料的晶体结构,使得其比表面积和无序程度增加;FT-IR研究表明,高能球磨使原料的键能减小.可见,高能球磨导致了原料内部贮能增加和反应活化能减小.球磨40 h的原料在900 ℃煅烧2 h可以得到单相钛酸锶,而未粉磨的需要1300 ℃.     

超细钛酸锶陶瓷粉体的湿化学制备技术

随着钛酸锶电子陶瓷应用日益广泛,对其性能要求不断提高,所以制备超细钛酸锶粉体的湿化学制备技术越来越受到重视,制备超细钛酸锶粉体的湿化学方法主要包括:沉淀法,金属醇盐水解法,溶胶-凝胶法,微乳液法,水热法,燃烧合成法.本文简要阐述这6种主要湿化学合成工艺的研究进展,介绍了它们的优缺点,对各种方法进行了比较.     

超声降解酚类污染物的研究

超声降解处理技术是一种很有发展前景的新兴有机含酚废水处理技术。介绍了超声波技术处理难降解酚类化合物的机理及影响处理效果的因素,以及近几年来超声协同其它技术降解含酚废水的最新研究成果。     

Effect of nickel addition on the physicochemical properties of SrTiO3-based materials

Synthesis of materials in Ni/SrTiO₃ system was undertaken. Perovskite structure material with nominal composition SrTi_0.98O₃ was synthesised by the sol-gel method. Nickel was introduced into the system by the wet impregnation method followed by proper thermal treatment. Two research paths were carried out: the evaluation of sintering conditions on material properties (sintering temperature: 1100, 1200, 1300 and 1400 °C; sintering time: 1, 3 and 5 h for sintering at 1300 °C) and the effect of nickel addition on the material properties - 1, 2, and 5 mol% of Ni compared to the amount of Ti was introduced into the analysed system. The microstructures of the materials, together with their structural (XRD analysis) and electrical (total conductivity and Seebeck coefficient) properties, were determined. Furthermore, temperature-programmed reduction (TPR) and temperature-programmed oxidation (TPOx) measurements were performed to evaluate the materials’ redox properties. It was shown that less than 1 mol% of Ni could be incorporated into the strontium titanate structure when a wet impregnation was chosen as the method for the introduction of Ni into the SrTiO₃-based system. NiO and, for the highest amount of introduced nickel, also NiTiO₃ were the main additional nickel-containing phases. For all materials synthesised in the Ni/SrTiO₃ system, the positive value of the Seebeck coefficient was observed, suggesting that nickel is an acceptor-type dopant while incorporated into the perovskite structure. However, the TPR measurements clearly imply that nickel can be incorporated into the strontium titanate structure in various oxidation states.     

Optical properties of multi-stacked BaTiO3/SrTiO3 thin films synthesized via chemical method

In this work, the BaTiO₃ and SrTiO₃ thin films as well as BaTiO₃/SrTiO₃ lamellar composites are synthesized via sol-gel spin-coating method. The formation of corresponding phases from their sols is investigated by virtue of X-ray diffraction on their powders, which confirms the formation of tetragonal structure for BaTiO₃, but cubic structure for SrTiO₃. The field emission scanning electron microscopy images show that crack-free films with different morphologies are formed in each sample. Likewise, by changing periodicity of the samples, the morphology of the composite samples is changed. As the number of layers increases from 1 to 20, the band gap reduces from 4.38 eV to 4.10 eV for BaTiO₃ samples and from 4.13 eV to 3.80 eV for SrTiO₃ samples confirmed by UV–Vis spectra. The band gap of periodicity = 1 sample is higher than that of BaTiO₃, while band gaps of periodicity = 2 and 5 composites mount between those of BaTiO₃ and SrTiO₃. In addition, the refractive indices of multi-stacked composites are about 0.2 lesser than refractive indices of BaTiO₃ sample in high wavelengths. The periodicity dependence of optical frequency dielectric constant, dielectric loss, impedance, Urbach tail, extinction coefficient, and electric modulus of multi-stacked composites are also studied.     

Effect of nanostructure on the thermal conductivity of La-doped SrTiO3 ceramics

A series of La-doped (10 at.%) SrTiO₃ ceramics with grain size ranging from 6 μm to 24 nm was prepared from nanocrystalline powders using high-pressure field assisted sintering (HP-FAST). A progressive reduction of thermal conductivity κ with decreasing grain size was observed. At room temperature, κ of the ceramic with grain size of 24 nm (1.2 W m⁻¹ K⁻¹) is one order of magnitude lower than that of undoped single crystals. The strong suppression of κ can be ascribed to (i) the high concentration of lattice defects, (ii) the increasing contribution of grain boundaries to phonon scattering when the grain size is decreased to the nanoscale and (iii) a moderate amount (10–15 vol.%) of nanopores. These results demonstrate that nanostructuration can be a successful strategy to attain a considerable reduction of κ in heavily doped bulk oxide ceramics. The low electrical conductivity of the La:SrTiO₃ nanoceramics represents a major obstacle for thermoelectric applications.     

Densification,microstructure, and thermoelectric properties of AZO/SrTiO3 composites

Al-doped ZnO (AZO) has emerged as a potential high-temperature thermoelectric material with an appropriate Seebeck coefficient and high thermal stability, and hence is considered as a promising material for power generation applications. Herein, we report the fabrication of AZO/SrTiO₃ composites with improved thermoelectric performance. The densification, microstructure, and thermoelectric properties of the AZO/SrTiO₃ composites were investigated. The significant increase in the relative density of AZO from 89.1 to 98.0% after the addition of SrTiO₃ indicates that SrTiO₃ promoted the densification of the composites. Furthermore, the electrical conductivity of AZO increased after the addition of SrTiO₃, which can mainly be attributed to its enhanced relative density. The AZO/SrTiO₃ composite with 2.0 wt% SrTiO₃ showed the highest power factor at 1000 K because of its highest electrical conductivity. In addition, the composite showed the highest ZT value, which was 1.8 times higher than that of pure AZO.     

Grain growth and segregation in Fe-doped SrTiO3: Experimental evidence for solute drag

In functional ceramics, the impact of dopants on bulk crystals is generally well understood. Their impact on grain boundaries is less well known. The present study investigates the impact of acceptor dopants on grain growth in strontium titanate. Scanning electron microscopy and analytical (scanning) transmission electron microscopy have been used to gain knowledge on Fe segregation behavior, grain sizes, and grain size distributions of SrTiO₃. While undoped microstructures show normal grain growth at low temperatures (<1350 °C), doped microstructures evolve bimodally. With increasing acceptor dopant concentration, an increasing population of small grains develops. It is shown that Fe segregates to the grain boundaries due to its negative charge and a positive boundary potential. Thus, the experimental findings seem to be well explained by the theory of solute drag: The diffusion of segregated defects (‘solutes’) at grain boundaries can retard grain boundary migration.